Wearable physiological detection sensors are commonly used to detect any number of physiologically relevant data, including but not limited to: heart rate, blood oxygenation, movement, and respiratory rate. These sensor devices were once most commonly associated with static workout machines, such as treadmills, stair climbers, bicycles, elliptical, rowing machines, and the like, however, sensing devices are now ubiquitous in many mobile electronic devices and wearable devices and are no longer required to be tethered to a static exercise machine. For example, most smart phones have a motion or step counter and, many wearable devices assist individuals with measuring their movement, heart rate, and other physiological components during the day and allow individuals to track, store, and mine physiological data throughout the day, or over weeks, months or years. Furthermore, these devices allow for synching of data from one or more sensors and activities, which allows for a greater evaluation of the physiological profile of the user with certain applications and software.
A common feature on static exercise machines is a program to assist a user with reaching and maintaining a target heart rate over a pre-determined amount of time. The target heart rate is often cited as 60% to 75% of maximum heart rate for a “fat-burning zone” and 75% to 85% of maximum heart rate in the so called “aerobic” workout zone. Accordingly, many workout machines, in conjunction with a heart rate monitor, increase or decrease resistance or otherwise modify the exercise program to maintain heart rate within a certain range. Thus, these programs seek to guide users to a certain heart rate based on the age and/or weight of the individual to assist with greater fat loss or aerobic workout, as these “fat burning zones” have not proven to effectively burn greater amounts of fat in all users than higher intensity workouts.
However, the ranges utilized by these programs, specifically the “fat-burning zone,” do not necessarily correlate with actual fat burning. Instead, these programs provide users with a program to maintain a particular intensity, usually at a lower heart rate than maximum, and thus corresponding to a reduction in caloric expenditure during the exercise activity as compared to a program aimed at the “aerobic” range. Therefore, lower intensity results in lower caloric burn and thus may not be appropriately aiding the user in burning more fat or more calories as intended.
Ultimately, breakdown of fat and expenditure of calories occur when an individual depletes free energy sources and requires the use of stored fat for metabolic processes. Indeed, the body requires food sources as energy to function. Specifically, certain forms of carbohydrates and glucose provide for a general fuel in cell metabolism. A benefit of carbohydrate or glucose based energy sources is that they are generic, in that they can be metabolized by any cell. Glucose is a readily available energy source and can be obtained directly from food ingested and digested by the body. Furthermore, glucose can be generated by breaking down other carbohydrates within the body when fuel is needed. As the human body cannot constantly process and digest food from the stomach and intestines, it is imperative that some sources of energy can be stored to provide energy for necessary metabolic function.
The body stores certain reserves of energy, such as glycogen and as fat, to maintain sufficient energy reserves for metabolic function. In humans, glycogen is made and stored primarily in the cells of the liver and the muscles, where it is hydrated with three or four parts water. Fats are held in adipose tissue, and ultimately make up the primary storage of energy in the body. Both types of stored energy can be broken down by the body and utilized when the body needs fuel for metabolism.
In the mammalian body, when glycogen reserves are depleted, glucose can be obtained from the breakdown of fatty acids in the liver by the process of beta oxidation to produce ketone bodies for fuel. During fasting, strenuous exercise, or in persons with low glucose levels, fatty acids therefore can be used as a direct source of energy. The byproduct of fatty acids being utilized for energy are ketone bodies. Ketone bodies consist of molecules of acetone, acetoacetic acid and beta-hydroxybutyric acid. The human body can use two of these, acetoacetic acid and beta-hydroxybutyric acid directly, but cannot directly use acetone as a source of energy. Acetone is only partially metabolized in the body, for example by CYP2E1, but it is often eliminated from the body via sweat or urine. Therefore, Acetone is recognized as a byproduct of fat breakdown in the body.